Oversized watches with sturdy pendants for hanging them in moving conveyances became popular among the wealthy in the second half of the seventeenth century. They are thus often called coach watches. In this splendid example, there are separate going, striking, and alarm trains, each with its own power source, and the watch incorporates the recently invented balance spring, the hair-thin spiral attached to the balance wheel, which, in turn, is secured by the delicately pierced and engraved cock visible on the back plate. Tompion experimented for a short time with substituting the action of a balance spring for that of a fusee. This watch is one product of the experiment, and it has no fusee.

The dial, visible through the glass lens, is silver chased in low relief in a technique known as champlevé. It has two concentric chapter rings separated by a band of floral-ornamented arabesques: the outer ring with Roman numerals (I–XII); the inner ring, part of a separate disk, with Arabic numerals (5–60). For setting the alarm, the disk of the inner ring can be manipulated so that the hand attached to the edge points to the desired hour. The actual time is indicated by the single concentrically driven hand that points to the scale in Arabic numbers on the disk, adhering to the old format of a single hand showing only hours and quarters to be found on most pre-balance spring watches.